Zalophus californianus
California Sea Lions are mammals. They must breathe at the surface and hold their breath while underwater, so they are specially adapted to live both on the land and in the sea. Their hind flippers act like rudders in the water but can be rotated under the body to walk on land to help them climb on the rocky shorelines.
To learn more about California Sea Lions visit them at the Helmerich Sea Lion Cove.